AMONG THE VARIOUS KINDS OF EXPERIMENT undertaken by amateurs, experiments in animal behavior are fairly rare. The reason may be that the potential experimenter, being himself a member of the animal kingdom, realizes that animals are complex systems and rather unpredictable. The fact remains that experiments in animal behavior can be profitably performed by the amateur, provided he is modest and realizes that his results may not be as conclusive as, say, an elementary experiment in physics.

A case in point is an experiment in the behavior of chicks performed last year as a science-fair project by Elizabeth Neville of Calgary, Alberta. At the time Miss Neville was only 13! In describing her experiment it will be helpful to consider first two similar kinds of experiment in the literature of animal behavior.

A traditional question about animal psychology concerns whether or not animals perceive colors the way human beings do. In one classic experiment Karl von Frisch of Austria demonstrated that honeybees can distinguish between blue and white. The insects were first trained to feed on sirup that had been placed against a blue background. Sirup was then applied to a blue square set in a checkered design of gray squares that ranged in tone from near-white to near-black. Frisch reasoned that the intensity of light reflected by a particular gray square of the series would match the intensity of the blue square. Unless the bees were endowed with a color sense they would be unable to distinguish the blue square from the matching gray square. When the insects were released, the majority flew directly to the colored square, a positive response indicating that honeybees do perceive blue. In subsequent experiments other investigators substituted translucent windows of various colors for Frisch's opaque squares. These experiments indicated that bees are blind to deep red but sensitive to bands of color in the yellow-green, blue-green and blue regions of the spectrum, and to ultraviolet radiation that is not perceived by the human eye.

Similar questions can be asked about how animals perceive form. Robert L. Fantz of Western Reserve University has described an experiment for determining the preference of newly hatched chicks for food particles of certain shapes, principally with the objective of discovering if such preferences are partly innate [see "The Origin of Form Perception," by Robert L. Fantz; SCIENTIFIC AMERICAN, May, 1961]. He first made up synthetic particles about the size of seeds in various two-dimensional and three-dimensional shapes. The two-dimensional particles ranged in form from circles to triangles and the three-dimensional ones from spheres to pyramids. To eliminate the influence of such factors as touch, taste and smell he enclosed each particle in a transparent capsule of plastic. The capsules were attached to sensitive switches in an electrical counting apparatus and arranged along one wall of a box within easy pecking reach of the chicks. The chicks were hatched in total darkness and tested before they encountered any food. More than 1,000 birds served as subjects. They pecked 10 times oftener at the sphere than at the pyramid. Objects about an eighth of an inch in diameter were preferred to other sizes. Among the flat forms circles were preferred to triangles. These results demonstrate that the chick is endowed with an inborn ability to discriminate shape and with the tendency to peck at those shapes that resemble the shape of its natural food.

Miss Neville's experiment took up the perception of both color and form. Do chicks have an innate preference for color as they do for form? If so, does the preference for color take precedence over preference for shape? As subjects for the experiment she selected 12 chicks about 20 hours old that had never eaten before. Her apparatus consisted of a box 24 inches long, 15 inches wide and six inches high. The food particles used in the experiment were made of moistened white bread pressed to a thickness of about one millimeter, dyed with food coloring and cut or molded into spheres, disks and equilateral triangles three millimeters in diameter. Another group consisted of triangles 1.5 millimeters thick but with the same diameter. She dyed 120 particles of each shape brown and 60 particles red.

Before running the first test Miss Neville checked the materials and procedure by offering the food particles to a group of chicks that was not used in the subsequent experiment. The check revealed that isolated birds refused to eat and that the particles were somewhat too large. The particle size was reduced to two millimeters. The experimental birds were then put into the text box in groups of six along with 120 dry brown food particles equally divided among spheres, disks and thin and thick triangles. The various shapes were mixed and distributed uniformly on the floor of the box. The birds refused to eat the food. They were removed after 15 minutes and the food was moistened. On being returned to the box the chicks began to eat and were allowed to do so for five minutes. During this interval they consumed 11 spheres, nine thin triangles, three thick triangles and two disks. Because of the strong preference shown for spheres and thin triangles the box was then stocked with 30 each of these two shapes in red and brown. The remaining six chicks were placed in the box for five minutes. The consumption was nine brown triangles, eight brown spheres, one red triangle and no red spheres. Statistically there is less than one chance in 100 that random pecking could account for this score.

Both experiments were repeated 24 hours later. Meanwhile the chicks had been given normal "starter" feed for 20 hours. The preference for brown spheres and brown thin triangles persisted, as in the first experiment. A second group of birds was then placed in the box along with 15 particles each of all shapes and both colors. The chicks ate with such vigor that they had to be removed at the end of two minutes. The score: 15 brown spheres, 12 brown disks, 12 brown thin triangles, 13 brown thick triangles, 11 red spheres, 11 red disks, seven red thick triangles and four red thin triangles.

"From these results," writes Miss Neville, "it appears that, when form is held constant, chicks show a significant preference for brown over red, which may be explained by an inborn preference for the natural color of seeds. The preference for brown over red was displayed even more prominently during the second experiment than the data suggest, because the birds pecked at the brown shapes first and did not start on the red ones until the brown became scarce. In the matter of preference for form the results do not agree with Fantz's observation that chicks prefer spheres to pyramids. This disagreement might be explained by the fact that spheres tended to roll out of the beaks of my newly hatched chicks, although they pecked at them frequently. The results of my second experiment are more closely in accord with Fantz's. By then the birds had developed some skill in eating. The experiments suggest that newly hatched chicks have an inborn preference for color and that their preference for color is stronger than it is for form. I should like to recheck these conclusions by an experiment based on a different concept but so far I have not succeeded in designing one."

A few years ago Guillermo Zuloaga, a geologist who lives in Caracas, Venezuela, took time off from his professional work to make a study of the thick haze known as the calina that annually reduces visibility to almost zero along the northern coast of South America (see "The Amateur Scientist," SCIENTIFIC AMERICAN, October, 1961). Zuloaga has now made a similar study of another aspect of the Venezuelan climate: the periodic wind called the alisio that blows the calina away.

"This story," he writes, "is about the surprising content of marine salts I found in the water of the first rains that fall after the long dry season in Venezuela, and the relation of these salts to the trade wind known in Spanish as the alisio.

"All along the coast of Venezuela, which stretches more than 1,000 kilometers at the southern edge of the Caribbean Sea, the alisio blows steadily from the northeast most of the year. The influence of this wind on our climate is enormous. Because of it we have a very mild climate. Were it not for the alisio Venezuela would be as hot and humid as countries in Africa and Asia at the same latitude. The name alisio comes from the Greek aliso, which means 'salting.' Possibly some erudite conquistador in the distant past gave this fitting name to our wind. It is about its 'salting' characteristic that I wish to comment.

"The calina forms when airborne droplets of water from the sea partially evaporate and leave microdrops of brine suspended in the lower atmosphere. The presence of the calina does not increase the relative humidity as measured by either the hair hygrometer or the wet-and-dry-bulb thermometer, but it creates the impression of high humidity; the air feels 'thick,' yet the relative humidity may measure less than 50 percent.

"Now we come to the study with which I have been lately amusing myself. On the afternoon of April 14 this year the air in Caracas was stifling. The temperature in my house reached 90 degrees Fahrenheit, almost a record for the city. The relative humidity was 50 percent. As I was driving downtown two or three drops of rain fell on the windshield of my car; I noticed that they dried almost immediately, leaving white spots. This sparked my curiosity. I hurried back home, attached a number of clean microscope slides to a little board and attached the board to the car so that the slides would be exposed to the air as I drove. For two hours I drove back and forth, but not another drop of rain fell. Fortunately our wet season was due, and on the afternoon of April 19 we had our first rain. It was not abundant, but I was ready for it and collected 250 milliliters of rainwater in trays and many drops on microscope slides. Some friends who were spending the day at the beach knew of my interest and collected additional specimens in clean ashtrays.

"The drops that fell on the microscope slides left patches of white when they dried, and I hurried to examine the patches under the microscope. In addition to a little ash and dust there were abundant crystals of common salt together with other crystals that took me some time to identify. These crystals turned out to be hydrated calcium sulfate, more commonly known as gypsum [see Figure 1]. The collected water was filtered and boiled down to about a third of its volume. I sent some to a friend for spectroscopic examination; with the remainder I made drops and let them dry. In every case I obtained abundant salt crystals. The smaller crystals were gypsum, and there were still smaller ones I could not positively identify.

"The presence of gypsum came as something of a surprise. I had not identified it in the calina. Following the lead that the calina originates in the sea, I drove down to the beach and collected a specimen of seawater. The drops crystallized on the microscope slide as I watched-a fascinating phenomenon to observe. Crystallization proceeds not in the order of the abundance of the different salts but in the order of their decreasing solubility. To identify the respective substances I had to refresh my memory on the chemical composition of seawater and the solubility of its contents. When about 80 percent of seawater has evaporated, gypsum begins to crystallize out of it. Gypsum makes up only about 2.5 percent of the solids in solution. Common salt, or sodium chloride, appears when the volume of the water has been reduced about 90 percent. Actually I found a considerable overlap in the crystallization process. The retreating edge of the drops, as seen in the microscope, had a rapidly growing band of both common salt and gypsum, the salt in cubes and the gypsum in thin plates. Both large cubes of common salt and the branching crystals called dendrites were forming in the center of the drop at the same time as the gypsum. Quantitative analysis of the rainwater indicated a sodium concentration of 17 parts per million; this concentration, added to the concentration of chlorine, would make a solution about 1,000 times more dilute than seawater. Other elements present in the rainwater were calcium, magnesium, zinc, silicon, boron, iron, aluminum and other metals found in seawater.

"For the last experiment in the series I picked up a few drops of morning dew from the grass in my garden. On letting these dry I was amazed to find a high concentration of salts, and particularly to observe how deliquescent they were. I had to put the slides on a hot plate for two hours before even partial crystallization occurred. Evidently our dew contains a higher proportion of magnesium chloride to sodium chloride than rainwater does.

"As the alisio developed and more rains came I collected drops from a series of rains. It would seem that the alisio does not simply blow the calina away; the rains that come with the alisio wash the calina out of the air. The calina is not entirely washed out by a few short rains When the alisio diminished and the weather cleared for a few days, the concentration of salt in the atmosphere built up. The last traces did not disappear until the rainy season was in full swing.

"One is tempted to speculate on what effect the salty rains of the alisio have on the vegetation in this part of the world. One might at first assume that the effect would be uniformly adverse. That this assumption may be wrong is suggested by two recent conversations I have had with botanists. Plants do, after all, require not only water but also small quantities of mineral nutrients. One botanist remarked that the salt content of the alisio rains might at last explain why Venezuela has such thriving epiphytes: plants that grow not in the soil but aloft on trees or even on telephone wires. The mineral nutrients needed by the epiphytes may be airborne in the alisio rains. The other botanist simply mentioned a saying of the local farmers: 'A good rain after the dry season is better than a thousand waterings.'"

An amusing device that appears to defy gravity can be assembled in a few minutes from a pair of stoppered bottles, a funnel, a pair of glass tubes and a short length of rubber hose. First two holes are made in each stopper. The funnel is thrust through a hole in one stopper so that the spout comes close to the bottom of the bottle. A length of glass tubing is heated at one end and stretched to form a nozzle about a millimeter in diameter. The open end of the tube is pushed through the second stopper so that it comes close to the bottom of that bottle. The remaining holes in the stoppers are used for interconnecting the air spaces in the two bottles through glass nipples and the rubber tubing, as shown in the illustration on the left. All the connections must be airtight. The bottle that contains the nozzle is filled with water and supported so that it is about a foot higher than the empty bottle.

Now for the action. Prime the apparatus by pouring an ounce or two of water into the funnel. A slender stream will promptly spout from the nozzle and rise several inches higher than any part of the apparatus. If the stream is directed into the open mouth of the funnel, the level of the water in the funnel will thereafter remain constant, apparently circulating endlessly through the apparatus. Can this be perpetual motion? The explanation will soon become evident to those who perform the experiment. The inventor of this ingenious fountain, Hero the Elder of Alexandria, enjoyed puzzling friends with it some 2,000 years ago. The effect can be made more pleasing by directing the nozzle straight up from the center of the funnel. The jet then functions as a classical fountain. This modification requires a longer glass tube for the nozzle, and two bends. If you do not happen to have a funnel of the type shown above, just extend the spout of an ordinary funnel by coupling a glass tube to it through a short length of rubber hose.

Bibliography

HALF-HOURS WITH GREAT SCIENTISTS. Charles G. Fraser. Reinhold Publishing Corporation, 1948.

PHYSICAL METEOROLOGY. John C. Johnson. John Wiley & Sons, Inc., 1954.

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